Not that looking back is necessary for predicting this year’s winner. Martin Scorsese should finally capture the prize that has eluded him for decades, despite having been nominated for such classics as ‘‘Raging Bull’’ and ‘‘Goodfellas.’’ ...

Scorsese’s ‘‘The Departed,’’ about cops and mobsters outsmarting each other in Boston, is a return to the kind of gritty material that made him legendary. Come Oscar night, the sixth time should be the charm. (In a discussion of Oscar-winning movies coming in two sizes, large and small, ‘‘The Departed’’ would fall on the epic side.)

‘‘The single most powerful factor at the Oscars is the overdue director syndrome,’’ said O’Neil, who’s written several books about awards shows. ‘‘We saw this happen a few years ago when Roman Polanski managed to surmount all his bad PR problems and woes to win best director [for ‘The Pianist’] over Rob Marshall, who directed the best picture of the year, ‘Chicago.’ ...

‘‘When they gave it to Ang Lee last year, is was partly the same thing. He was an overdue director,’’ he added, noting that Lee directed 2000’s foreign-film Oscar winner in ‘‘Crouching Tiger, Hidden Dragon’’ — which also was up for best picture that year.

And when 2001’s ‘‘A Beautiful Mind’’ won best picture, despite criticism that it sugarcoated the life of mathematician John Nash, it still won best director ‘‘because Hollywood was that determined to catch up with Ron Howard,’’ O’Neil said.

Robert Wilonsky, film critic for the Village Voice chain of weekly newspapers, said directors win the Oscar ‘‘for being great ringmasters of spectacles in a lot of cases.’’

‘‘Someone like Clint Eastwood or Jim Cameron or Peter Jackson [‘The Lord of the Rings: The Return of the King’] especially is someone who keeps tight control over what could be a chaotic and disastrous set,’’ said Wilonsky, host of the movie show ‘‘Higher Definition’’ on HDNet. ‘‘Occasionally that’s all a director does. A director doesn’t determine how a film looks, that’s the cinematographer. The director didn’t write the thing. The director makes sure stuff doesn’t fall apart. They’re awarded for making sure the process doesn’t break down, which is fine.’’

The directors who’ve won over the past decade have all been well-known and established, except for Mendes, whose ‘‘American Beauty’’ (1999) was his first feature.

If there’s any common thread to the last 10 years of winners, O’Neil said, ‘‘they’re all heroic figures as directors: James Cameron, even Anthony Minghella with ‘The English Patient,’ and Spielberg. They are such huge stars off-camera that they still have huge presence over the film.’’

But looking back even further at Oscar history, the kinds of films that win for best director seem to go in cycles. Smaller movies in the late ’70s (Michael Cimino’s ‘‘The Deer Hunter,’’ Robert Benton’s ‘‘Kramer vs. Kramer,’’ Timothy Hutton’s ‘‘Ordinary People’’) gave way to blockbusters in the early ’80s (Warren Beatty’s ‘‘Reds,’’ Richard Attenborough’s ‘‘Gandhi,’’ Milos Forman’s ‘‘Amadeus’’). Lately, we’ve been in a small-movie phase.

Most of those films also were named best picture (1981’s ‘‘Chariots of Fire’’ won while Beatty took the directing prize). In the last eight years, though, the best-picture and best-director winners have differed half the time — and that could happen again this year.

While ‘‘The Departed’’ is likely to win best director, it seems any of the five films nominated could take home the top prize. Scorsese’s film is competing against ‘‘Babel,’’ ‘‘Letters From Iwo Jima,’’ ‘‘Little Miss Sunshine’’ and ‘‘The Queen.’’

‘‘It is ludicrous to suggest that the best picture of year isn’t the best directed. There shouldn’t even be a best director award — the director should share the best picture award with the producers,’’ said O’Neil. ‘‘There is no logic to this illogical split. Part of it is wanting to share the wealth. Last year you had two best pictures: They gave ‘Crash’ best picture and Ang Lee best director.’’

So who’s going to win this year?

O’Neil thinks Eastwood, who’s won two directing Oscars (for ‘‘Million Dollar Baby’’ and ‘‘Unforgiven’’) could play spoiler. Eastwood’s ‘‘Letters From Iwo Jima,’’ which looks at the Battle of Iwo Jima from the Japanese perspective, is a companion piece to his ‘‘Flags of Our Fathers.’’

‘‘The year [Steven] Soderbergh won for ‘Traffic,’ beating Ridley Scott for [best picture] ‘Gladiator,’ one of the chief reasons Soderbergh won was because he had two big movies, ‘Traffic’ and ‘Erin Brockovich,’’’ O’Neil said. ‘‘What does Clint have this year? Two big movies.’’

But Wilonsky would like to see a director win whose film isn’t even in the best-picture race: Paul Greengrass for ‘‘United 93.’’

‘‘There’s no piece of film this year more tense, more heartbreaking, more wrenching than ‘United 93,’’’ he said. ‘‘I had no interest in seeing that, and the fact that Paul Greengrass makes me want to see it a million times — I just think it’s an astounding achievement.’’